Quadrature signals, i.e. signals having the same frequency but a phase difference of 90.degree. (.pi./2), are used with many circuits and find particular application in circuits for fibre optic transmission systems and wireless communications. One important property of quadrature signals is that they can be multiplied to generate signals having a frequency that is double the frequency of the original signals. If the two quadrature signals are: EQU a=A sin (wt+.phi.)
and EQU b=A cos (wt+.phi.)
then by multiplying the two signals the result can be written: ##EQU1## where k is the multiplier gain.
The quadrature signals frequency doubler circuit of the present invention generates two quadrature output signals having a frequency equal to double the frequency of the two quadrature input signals utilizing conventional integrated circuit fabrication technology.